I use old lawn mower wheels. You could use old bike wheels, or watch TS when they have their $5 sale, they have 10" wheels then. Measure the hole in the wheel and get bolts that fit through it. Go bolt, washer, washer, wheel, washer, washer, frame, washer, nut, nut. Assemble all but the last nut. Tighten it down so it is snug, but not so tight to prevent the wheel turning. When you are happy with how it turns, put the second nut on tight. This will keep the 1st nut from loosening. You can put oil between the two washers if it tightens up later. I also attach a lawn mower handle to the end I am pulling. Sooo much easier! Cut a 2x4 the width between the end of the handle, I think about 16 or 18", screw the handle to the ends of the board. Then screw the board to the coop.